Trimmer condenser



April 1963 M. L. CROOKS 3,084,313

TRIMMER CONDENSER Filed April 28, 1961 Il' II /8 llllil I; 4 v 4 23 7 A! E 5" 7 E" 3 .l I 2/ ,i /0 F 20 w 22 FIG. 4

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United rates Patent 3,084,313 TRIMMER CONDENSER Marcius Lee Crooks, Erie, Pa., assignor to Erie Resistor Corporation, Erie, Pa., a corporation of Pennsylvania Filed Apr. 28, 1961, Ser. No. 106,383 2 tilairns. (Cl. 317-249) This invention is a trimmer condenser having accurately controllable adjusting torque and a high degree of stability in service.

In the drawing, FIG. 1 is a longitudinal section through a trimmer condenser, FIG. 2 is a side view, partly in section of the collet gripping the adjusting screw, FIG. 3 is an end view of the collet, FIG. 4 is a section through the spring which controls the pressure between the collet and the threads of the adjusting screw, and FIG. 5 is an end view of the spring.

The condenser has a tubular dielectric 1, for example of one of the glasses with a low temperature coefficient of expansion, having at one end a metal electrode coating 2 and having the opposite end telescoped over a cylindrical flange 3 on a bushing 4. The dielectric is fastened to the bushing 4 by a bead 5 of solder at the junction between a metal coating 6 on the dielectric and a radially projecting flange 7 on the bushing. For mounting purposes, the bushing has an externally threaded portion 8 and a nut 9. Other mounting constructions may be used. Within the bore of the dielectric is a cup shaped electrode member 10 of one of the metals having a low temperature coefficient of expansion. The bottom wall 11 of the electrode is fixed to one end of an adjusting screw 12 for moving the electrode along the bore of the dielectric. The parts so far described are or may be of common construction.

Surrounding the adjusting screw 12 is a collet 13 having at one end an externally threaded enlargement 14 screwed into an internally threaded section 15 in the bushing 8. Extending toward the opposite end of the collet are 4 spring fingers 16 conveniently formed by slots 17. At the extreme ends, the fingers are provided with inwardly extending projections 18, internally threaded to cooperate with the adjusting screw 12. On the outer surface, the ends of the fingers 15 have tapered surfaces 19 cooperating with spring fingers 20 of an annular spring member 21. The spring fingers 20 are conveniently formed by slots 22 extending in from one end of the spring member. The nnslotted end of the spring member 21 is seated on a shoulder 23 on the mounting bushing 8. The collet has a screw driver slot 24 by means of which it may be moved axially relative to the bushing 8 so as to force the tapered surfaces 19 on the collet against complementary surfaces on the spring fingers 20 of the spring 21. This provides free a precise and accurate control of the force exerted by the spring fingers 20 on the collet tending to move the threaded portion 18 of the collet radially into engagement with the adjusting screw 12. The radial clamping force between the threaded portions 18 on the collet and the adjusting screw takes up backlash and provides sufficient friction to prevent unwanted change in position of the adjusted screw. The desired friction grip on the adjusting screw is easily controlled by the torque exerted at the screw driver slot 24. In addition to exerting a radial clamping force on the adjusting screw, the spring fingers 20 also exert an axial force tending to take up any backlash between the externally threaded section 14 of the collet and the internal threads 15 in the mounting bushing. Once the desired friction grip on the adjusting screw 12 has been set, the collet may be suitably anchored to the mounting bushing, for example by staking.

What is claimed as new is:

1. A trimmer condenser having a tubular dielectric fixed at one end to an internally threaded tubular mounting bushing, an external electrode on the dielectric, an internal electrode, an adjusting screw for moving the internal electrode along the bore of the dielectric, a collet having one end externally threaded and screwed into the internally threaded bushing and having spring fingers at the opposite end internally threaded to cooperate with the adjusting screw, said fingers having external wedge surfaces, spring means surrounding the collet and having one end fixed relative to the bushing and the opposite end engaging the wedge surfaces on the collet to force the spring fingers of the collet inward to grip the adjusting screw, said collet being provided with means by which it may be screwed into and out of the bushing to adjust the force of the spring on the wedge surfaces on the collet.

2. A trimmer condenser having a tubular dielectric fixed at one end to an internally threaded tubular mounting bushing, an external electrode on the dielectric, an internal electrode, an adjusting screw for moving the internal electrode along the bore of the dielectric, a collet having one end externally threaded and screwed into the internally threaded bushing and having spring fingers at the opposite end internally threaded to cooperate with the adjusting screw, said fingers having external wedge surfaces, a tubular spring member surrounding the collet having one end fixed relative to the bushing and having spring fingers at the opposite end engaging the wedge surfaces on the collet to force the spring fingers of the collet inward to grip the adjusting screw, said collet being provided with means by which it may be screwed into and out of the bushing to adjust the force of the spring on the wedge surfaces on the collet.

No references cited. 

1. A TRIMMER CONDENSER HAVING A TUBULAR DIELECTRIC FIXED AT ONE END TO AN INTERNALLY THREADED TUBULAR MOUNTING BUSHING, AN EXTERNAL ELECTRODE ON THE DIELECTRIC, AN INTERNAL ELECTRODE, AN ADJUSTING SCREW FOR MOVING THE INTERNAL ELECTRODE ALONG THE BORE OF THE DIELECTRIC, A COLLET HAVING ONE END EXTERNALLY THREADED AND SCREWED INTO THE INTERNALLY THREADED BUSHING AND HAVING SPRING FINGERS AT THE OPPOSITE END INTERNALLY THREADED TO COOPERATE WITH THE ADJUSTING SCREW, SAID FINGERS HAVING EXTERNAL WEDGE SURFACES, SPRING MEANS SURROUNDING THE COLLET AND HAVING ONE END FIXED RELATIVE TO THE BUSHING AND THE OPPOSITE END ENGAGING THE WEDGE SURFACES ON THE COLLET TO FORCE THE 